During the past few years many lives have been saved through the effective use of Cardio Pulmonary Resuscitation (CPR) techniques. In incidents of heart failure or fibrillation and interruption of natural breathing as brought about by electric shock or other causes, these natural functions are often restored by means of artificial circulation (external cardiac compression) and mouth-to-mouth resuscitation.
In the administration of the CPR technique, the victim's heart is compressed by means of a gradually applied pressure exerted against the sternum, sufficient pressure being applied to drive the sternum one and one-half to two inches toward the spine, and thereby to cause blood to be exhausted from the ventricles. The pressure is then released to allow the return of blood to the auricles. The compression stroke is applied by the palm of one hand assisted by the other hand placed on top of the first, and it is applied repeatedly at a steady rate approximating the normal heartbeat. Because such heart failure is almost invariably accompanied by interruption of the breathing function, mouth-to-mouth resuscitation is given at the same time. If only one rescue person is involved, two breathing cycles are applied for every fifteen heart strokes. It two persons are available to perform rescue operations, one applies external cardiac compression while the other gives mouth-to-mouth resuscitation.
Because of increased publicity and education regarding these techniques and their efficacy in restoring such victims, CPR has been credited with the saving of increasing numbers of lives in recent years.
At the same time, it is evident that a still higher degree of success can be achieved through improved educational methods and equipment and through the provision of any other means which might assure the optimum application of the CPR technique with less dependence upon the skill or practice of the rescue personnel. It is difficult for someone of limited experience, for example, to know when he is applying sufficient pressure. It is also especially difficult to judge whether such proper pressure is being sustained as fatigue begins to be felt by the person administering the technique.
It is clear, therefore, that an effective mechanical aid for gauging the pressure applied to the sternum, in turn compressing the heart, is urgently needed and that such a device might realistically be expected to save many lives.